(a) Technical Field of the Invention
The present invention relates to alloy rim, and in particular, to a method of manufacturing alloy rim for use in automobiles.
(b) Description of the Prior Art
Conventional methods for manufacturing of alloy rim are disclosed in U.S. Pat. Nos. 4,589,177 and 4,185,370. The U.S. Pat. No. 4,185,370 discloses an improved method of making vehicle wheel rims particularly suitable for use with materials having relatively low ductility, such as aluminum. A circumferential drop center well is formed about the periphery of the band and work hardened so that the well material exhibits higher strength and lower ductility than the remaining band material. The strength and ductility differential between the well and band material adjacent thereto assists in confining material movement in subsequent rim forming operations and induces drawing of the rim bead seat area material
U.S. Pat. No. 4,589,177 discloses a method of manufacturing a wheel rim for a motor vehicle, including cutting off a section of an extruded cylindrical tube to produce a hollow cylindrical rim blank, and subjecting the blank to two successive deformation steps. During the first step, only the central section of the blank is deformed radially inwardly, the diameter of the end sections remaining substantially unchanged. In the second step, only the edge portions of each end section are deformed radially outwardly, so that the region between each edge portion and the central section is unchanged in diameter. Also, the outermost part of each edge of the blank is bent into a U-shape. The rim is then gauged to finish it. The first deformation step is performed by a pair of cooperating rollers having central sections shaped to deform the central section of the blank. The end sections of the rollers are spaced apart to accommodate the end sections of the blank, the spaces being open at the sides of the rollers to permit free endwise flow of the rim blank outwardly from between the rollers.
The drawbacks of these methods are that a plurality of different shape rollers and molding devices have to be employed in order to produce the required cross-sectional shape of the alloy rim. As a result, the process of manufacturing is slow and laborious and the cost of production is high.
Another drawback of the conventional method is that the density of the material used for alloy plate is low and in the course of roller pressing on the alloy plate, the force distribution may not even and therefore the size of bubble on the surface of the alloy is large, and if a high speed tire is fitted onto the alloy rim, air leakage may occur when the tire is pumped with a high pressure.
Accordingly, it is an object of the present invention to provide a method of manufacturing alloy rim for automobile, which mitigates the above drawbacks.